Thanks for the replies folks. I would love to give OpenBSD a try, but the laptop I'm getting is rather new and fancy, and I suspect not all of it would be supported. Plus it's a new ecosystem and I don't have the time to learn it all at the moment (this is my work machine, too). I'll have to learn my way around it in qemu sometime soon. Same for 9front, now I think of it.
I'm glad to hear Gentoo is more solid these days. Kamil, your point about security updates is a good one, though at the moment running Debian stable doesn't feel particularly secure to me (using surf on the system-supplied webkit, which has many known vulnerabilities, because I haven't yet had the heart to build it for myself, and in general running various oldish software from Debian which almost certainly has known holes that haven't been marked as security-sensitive and fixed in Debian). But yes, that, plus the desire to not have to switch distributions because one or two peoples' priorities have changed, makes me wary of going for a small distro. Devuan I had not heard of. Sounds nice, and the dyne people seem to be very good people, but I wonder whether it suffers the problems above of being scarily small. Maybe not, if they mostly just use Debian's repos, I don't know. parazyd, any comment on that? Anyway, thanks for all the thoughts, I'm currently leaning towards Gentoo or Debian/Devuan (I am secretly conservative and boring at times), but who knows where I'll end up. Love to you all. Nick